The invention presented herein relates to electrographic stylus recording apparatus which involves the supply of toner powder from a hopper to a recording region between a stylus electrode and a receptor recording member as electrical signals are selectively applied to the stylus and, in particular, to apparatus for removing excess toner powder from the recording region and receptor recording member for return to the toner powder hopper.
U.S. patent application Ser. No. 269,069, filed June 2, 1981, now U.S. Pat. No. 4,402,000, a continuation patent application of U.S. patent application Ser. No. 22,859, filed Mar. 29, 1979, (now abandoned) by G. W. Fabel et al, discloses an electrographic apparatus for maintaining a controlled quantity of magnetically attractable, electronically conductive toner powder in a recording region formed between an array of stylus electrodes and a receptor recording member which makes electronic contact with a grounding electrode. A regular or relatively uniform supply of toner powder is provided from a supply of toner powder in a hopper to the recording region where a magnetic force is presented which acts on the toner to establish an electronically conductive path via the toner between the stylus electrodes and the recording member. Recording electrical potential signals are selectively applied to the stylus electrodes relative to the grounding electrode to cause toner to be deposited on the recording member as image toner. The apparatus provides for removal of excess accumulated toner from the recording gap, with such toner returned to the toner supply. The patent application teaches the use of a magnetic member disposed at the stylus electrode to provide the magnetic force mentioned above which also acts to draw excess accumulated toner away from the recording gap. It is indicated that the toner drawn to the magnetic member can be removed by a vacuum pull-off system, with such toner then being available for reuse. Mechanical augers and belt skiving mechanisms are other approaches indicated for removing such toner from the magnets for reuse. Such arrangements for removing the toner are overly complex and have been found to be abrasive on the toner. Such arrangements for removing toner limit the extent to which the toner can be used repeatedly when the apparatus is used to produce unfixed or nonpermanent toner images which are not transferred from the receptor recording member.